Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$11.37	6.327%	$12.0894	$12.09	$12.10	$12.10
Purchase #2	$104.61	6.298%	$111.1983	$111.20	$111.20	$111.20
Purchase #3	$153.53	6.853%	$164.0514	$164.05	$164.05	$164.10
Purchase #4	$235.55	9.722%	$258.4502	$258.45	$258.45	$258.50
Purchase #5	$145.77	4.493%	$152.3194	$152.32	$152.30	$152.30
Purchase #6	$140.57	12.838%	$158.6164	$158.62	$158.60	$158.60
Purchase #7	$77.88	11.363%	$86.7295	$86.73	$86.75	$86.70
7 purchase totals =	$869.28		$943.4546	$943.46	$943.45	$943.50